Conventionally, an LCD device includes a backlight module, a liquid crystal panel, and a frame for accommodating the backlight module and the liquid crystal panel.
FIG. 6 shows a schematic, top view of a conventional LCD 300. The LCD 300 includes a flexible printed circuit (FPC) board 310, a liquid crystal display panel 320, a rubber frame 330, two light emitting diodes (LEDs) 340 cooperatively serving as a light source, and a light guide plate 400.
The FPC 310 connects with the liquid crystal display panel 320, and includes a main circuit area 311 and a light source setting area 312. The light source setting area 312 is an appending portion extending from the main circuit area 311. The LEDs 340 are arranged on the light source setting area 312. The frame 330 includes a depressed portion 331, and the depressed portion 331 has two openings 332.
The LCD 300 can be assembled according to the following sequence: firstly, setting the light guide plate 400 inside the frame 330; secondly, arranging the light source setting area 312 into the depressed portion 331, and placing the LEDs 340 into the openings 332; thirdly, folding the main circuit area 311 to the frame 330 and the light guide plate 400; and lastly, folding the liquid crystal display panel 320 to the frame 330.
However, the above-mentioned conventional liquid crystal display has the following problems.
The sizes of the openings 332 may not precisely match the sizes of the LEDs 340 due to imprecise manufacturing. When this happens, small gaps exist between the LEDs 340 and the light guide plate 400 after assembly. These gaps may diminish the emitting luminance of the light guide plate 400. In addition, the FPC 310 easily bends, thereby changing angles between the LEDs 340 and the light guide plate 400. This can reduce the uniformity of the emitting luminance.
FIG. 7 is a graph showing the negative impact of the above mentioned gaps on the effective utilization of the emitting luminance. X represents the distance between the LEDs 340 and the incident surface (not labeled) of the light guide plate 400 in millimeters (mm), and Y represents the relative emitting luminance of the light guide plate 400 as a function of X. It can be seen that the greater the value of X, the lower the value of Y. That is, the greater the gap, the lower the value of the relative emitting luminance.
What is needed, therefore, is a backlight module and a liquid crystal display device using the same that overcome the above-described deficiencies.